Field of the Invention
This disclosure relates generally to the field of gasification. More specifically, the disclosure relates to a system and method for the production of synthesis gas via gasification of carbonaceous materials. Still more specifically, the disclosed system and method provide for enhanced gasification of carbonaceous materials via incorporation of alternative gasifier fluidization gas in place of, or in addition to, steam.
Background of Invention
Gasification is utilized to produce process gas suitable for the production of various chemicals, for the production of Fischer-Tropsch liquid hydrocarbons, and for the production of power. Many feed materials may serve as carbonaceous sources for gasification, including, for example, shredded bark, wood chips, sawdust, sludges (e.g., sewage sludge), municipal solid waste (MSW), refuse-derived fuel (RDF), and a variety of other carbonaceous materials.
Fischer-Tropsch (FT) synthesis represents a catalytic method for the creation of synthetic liquid fuels. The reaction occurs by the metal catalysis of an exothermic reaction between carbon monoxide and hydrogen gas in mixtures known as synthesis gas, or ‘syngas’. The liquid product of the reaction is typically refined to produce a range of synthetic fuels, lubricants and waxes. The primary metals utilized as catalysts are cobalt and iron. Providing synthesis gas having a desired molar ratio of hydrogen to carbon monoxide is necessary for economic production of Fischer-Tropsch synthesis products.
One concern when producing synthesis gas via gasification is the moisture content thereof. For example, excessive amounts of water vapor in the gasification product gas may be undesirable for numerous synthesis gas end uses, such as, but not limited to, Fischer-Tropsch synthesis, power generation, and the production of non-Fischer-Tropsch chemicals.
Accordingly, there is a need in the art for improved systems and methods of gasification, whereby gas produced elsewhere in the gasification may be utilized to advantage as fluidization gas for a fluidized bed pyrolyzer, thus reducing the amount of steam required therefor. Desirably, such improved systems and methods enable utilization of an alternate gasifier fluidization gas that may (e.g., tailgas) or may not (e.g., product synthesis gas) otherwise be considered a waste product, the utilization of the alternate gas enables the production of additional synthesis gas therefrom, the utilization of the alternate gas alters the composition (e.g., the ratio of hydrogen to carbon monoxide in the synthesis gas produced thereby) of the resulting gasifier product gas in a desirable manner, or some combination thereof.